The present invention relates to a computer system including a virtualization system and more particularly to technique of deciding a migration method (means and execution order) of a virtual server.
Virtualization systems include, as disclosed in, for example, JP-A-2004-234114 and US2007/0169121A1, means for migrating a virtual server between virtualization systems for the purpose of failover upon occurrence of physical trouble and load dispersion. The migration means each have different stop time, execution speed and necessary resources and accordingly a manager decides the migration means for each of virtual servers beforehand in consideration of availability of work operated in each virtual server.